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    <title>clGetExtensionFunctionAddress</title>
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      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="clGetExtensionFunctionAddress"></a>
        <h1>clGetExtensionFunctionAddress</h1>
        <p>
            Returns the address of the extension function named by <code xmlns="http://www.w3.org/1999/xhtml" class="varname">funcname</code>.
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
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              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">
                   <a class="link" href="scalarDataTypes.html" target="_top">void*</a>
                    <strong class="fsfunc">                   
                        clGetExtensionFunctionAddress
                    </strong>
                (</code>
                <td>const <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">char</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*funcname</var><code>)</code></td>
              </td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                    <code class="varname"> 
                        funcname
                    </code>
                </span>
            </dt>
            <dd>
              <p> 
                        Name of an extension function.
                    </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="description"></a>
        <h2>Description</h2>
        <p>
The function <code class="function">clGetExtensionFunctionAddress</code>
returns the address of the extension function named by <code class="varname">funcname</code>. The pointer returned should be cast to a function pointer type matching the extension function's definition defined in the
appropriate extension specification and header file. A return value of NULL indicates that the
specified function does not exist for the implementation. A non-NULL return value for
<code class="function">clGetExtensionFunctionAddress</code> does not guarantee that an extension function is actually supported. The application must also make a corresponding query using
<a class="citerefentry" href="clGetPlatformInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetPlatformInfo</span></span></a>(platform, <code class="constant">CL_PLATFORM_EXTENSIONS</code>, ... ) or <a class="citerefentry" href="clGetDeviceInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceInfo</span></span></a>(device,
<code class="constant">CL_DEVICE_EXTENSIONS</code>, ... ) to determine if an extension is supported by the OpenCL
implementation.
        </p>
        <p>
<code class="function">clGetExtensionFunctionAddress</code> may not be queried for core (non-extension) functions in OpenCL. For functions that are queryable with <code class="function">clGetExtensionFunctionAddress</code>,
implementations may choose to also export those functions statically from the object libraries
implementing those functions. However, portable applications cannot rely on this behavior.
        </p>
        <p>
Function pointer typedefs must be declared for all extensions that add API entrypoints. These
typedefs are a required part of the extension interface, to be provided in an appropriate header
(such as <code class="code">cl_ext.h</code> if the extension is an OpenCL extension, or <code class="code">cl_gl_ext.h</code> if the
extension is an OpenCL/OpenGL sharing extension).
        </p>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
  Since there is no way to qualify the query with a device, the function pointer returned must work for all implementations of that extension on different devices. The behavior of calling a device extension function on a device not supporting that extension is undefined.
        </p>
      </div>
      <div class="refsect2">
        <a id="example1"></a>
        <h3>
            Example
        </h3>
        <p>
The following convention must be followed for all extensions affecting the host API, where TAG can be KHR, EXT or vendor-specific:
</p>
        <div class="informaltable">
          <table border="0">
            <colgroup>
              <col align="left" class="col1" />
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              <tr>
                <td align="left">#ifndef extension_name
#define extension_name       1

// all data typedefs, token #defines, prototypes, and
// function pointer typedefs for this extension

// function pointer typedefs must use the
// following naming convention
typedef CL_API_ENTRY return type
      (CL_API_CALL *clextension_func_nameTAG_fn)(...);
      
#endif // extension_name
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
Consider, for example, the <a class="citerefentry" href="cl_khr_gl_sharing.html"><span class="citerefentry"><span class="refentrytitle">cl_khr_gl_sharing</span></span></a> extension. 
This extension would add the following to cl_gl_ext.h::
</p>
        <div class="informaltable">
          <table border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">#ifndef cl_khr_gl_sharing
#define cl_khr_gl_sharing     1

// all data typedefs, token #defines, prototypes, and
// function pointer typedefs for this extension
#define CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR -1000
#define CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR 0x2006
#define CL_DEVICES_FOR_GL_CONTEXT_KHR 0x2007
#define CL_GL_CONTEXT_KHR 0x2008
#define CL_EGL_DISPLAY_KHR 0x2009
#define CL_GLX_DISPLAY_KHR 0x200A
#define CL_WGL_HDC_KHR 0x200B
#define CL_CGL_SHAREGROUP_KHR 0x200C

// function pointer typedefs must use the
// following naming convention
typedef CL_API_ENTRY cl_int
     (CL_API_CALL *clGetGLContextInfoKHR_fn)(
              const cl_context_properties * /* properties */,
              cl_gl_context_info /* param_name */,
              size_t /* param_value_size */,
              void * /* param_value */,
              size_t * /*param_value_size_ret*/);
#endif // cl_khr_gl_sharing
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />
                                                 
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.1.pdf#page=266" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
            <a class="citerefentry" href="EXTENSION.html"><span class="citerefentry"><span class="refentrytitle">EXTENSION</span></span></a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2010 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials.
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